Gas turbine with an air bleeder tube

ABSTRACT

A gas turbine provided with an air bleeder tube ( 1 ) that, during startup, bleeds a portion of the compressed air of a compressor from the compressor and discharged the bled air into a cylindrical exhaust duct ( 20 ), wherein the air bleeder tube ( 1 ) is disposed at a portion that does not obstruct the flow of the main flow of combustion gas.

FIELD OF THE INVENTION

The present invention relates to a gas turbine.

BACKGROUND OF THE INVENTION

In the conventional gas turbine, it has been known a portion ofcompressed air bled from a compressor and a bled air is discharged intoan exhaust duct through an air bleeder tube (for example, PatentDocument 1 as described below).

FIG. 7 is a schematic view for showing one example of a conventional gasturbine. As shown in FIG. 7, the conventional gas turbine comprises arotor 10 for rotating around a rotational axis, a plurality of rotorblades 11 circularly mounted at the rotor 10, a turbine casing 12 forsurrounding and covering the rotor 10, a plurality of stator blades (notshown) mounted on the turbine casing 12, wherein the plurality of therotor blades 11 and the plurality of the stator blades are alternativelyarranged along the rotational axis. As shown as an arrow F in FIG. 7,the main flow of the combustion gas 13 is directed among them. Eachrotor blade 11 and each stator blade are made as one pair. These pairsmake a multi stage structure. FIG. 7 shows the rotor blade of the laststage located at the lower most side with respect to the main flow.

At the downstream side of the last rotor blade 11 with respect to themain flow, an exhaust diffuser 14 is coaxially connected. The exhaustdiffuser 14 of which an inside is connected to the main flow of thecombustion gas 13 comprises an exhaust casing 16 of which an insideforms a main flow of combustion gas 15 of which a cross sectional areais gradually enlarged along the direction of the main flow, a pluralityof struts for surrounding and supporting a bearing 17 for supporting therotor passed through the inside of the exhaust casing and manholes 19 inwhich an operator walks for a checking operation and a maintenanceoperation. At the downstream side of the exhaust diffuser 14 withrespect to the main flow, a cylindrical exhaust duct 20 is coaxiallyconnected.

In the conventional gas turbine, an air bleeder tube 100 is arrangedinside of an exhaust duct 20.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Utility Model Unexamined Publication No.6-60738

SUMMARY OF THE INVENTION Subject to be Solved by the Invention

However, the air bleeder tube 100 as described above is located in theexhaust duct 20. The air bleeder tube 100 obstructs the main flow ofcombustion gas as shown as an arrow F in FIG. 7. Thus, a ratio of thepressure loss is increased in the exhaust duct 20. As the result, aperformance of the gas turbine is reduced.

Upon reviewing the above drawback, a purpose of the present invention isto provide a gas turbine so as to improve a startup performance of acompressor at a startup timing, wherein a portion of the compressed airis bled from the compressor and the compressed air is discharged into anexhaust duct by an air bleeder tube of which a position does notobstruct the main flow of the combustion gas.

Means to Solve the Subject

To resolve the above subject, a gas turbine according to the firstinvention comprises a compressor and an air bleeder tube, wherein aportion of compressed air is bled from the compressor at a startuptiming and the compressed air is discharged into an exhaust duct throughthe air bleeder tube. The gas turbine according to the first inventionis characterized in that a main flow of combustion gas is not obstructedby an arrangement of the air bleeder tube.

To resolve the above subject, a gas turbine according the secondinvention is characterized in that the air bleeder tube is passedthrough an inside of an structural element connected to a bearing forsupporting a rotor.

To resolve the above subject, a gas turbine according to the thirdinvention is characterized in that the air bleeder tube is arranged at aportion immediately near a downstream end of a structural elementconnected to a bearing for supporting a rotor along the main flow ofcombustion gas.

To resolve the above subject, a gas turbine according to the fourthinvention is characterized in that an outlet of the air bleeder tube isarranged at a lower outer peripheral portion of a structural elementconnected to a bearing for supporting a rotor.

To resolve the above subject, a gas turbine according to the fifthinvention is characterized of further comprising three structureelements connected to a bearing for supporting a rotor, wherein thethree structural elements are arranged in an invert Y shape along aperipheral direction of a rotor and the air bleeder tube is passedthrough an inside of the structural elements.

To resolve the above subject, a gas turbine according to the sixthinvention is characterized in that the exhaust duct is a cylindricalshape and a rectangular exhaust duct of which a rectangular crosssection is connected to a lower end of the exhaust duct and the airbleeder tube may be arranged at each corner out of four corners of therectangular shape of an inlet end of the rectangular exhaust duct.

Effect of the Invention

According to the present invention, in order to improve a startupperformance of a compressor at a startup timing, a portion of compressedair is bled from the compressor and the compressed air is dischargedinto a cylindrical exhaust duct, wherein an air bleeder tube is disposedat a portion that does not obstruct the main flow of combustion gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a structure of a gas turbine according tothe first embodiment of the present invention.

FIG. 2 is a schematic view of a structure of a gas turbine according tothe second embodiment of the present invention.

FIG. 3 is a schematic view of a structure of a gas turbine according tothe third embodiment of the present invention.

FIG. 4 is a cross sectional view of the structure of the gas turbineaccording to the fourth embodiment of the present invention taken a linealong A-A in FIG. 1.

FIG. 5 is a schematic view of a structure of a gas turbine according tothe fifth embodiment according to the present invention.

FIG. 6 is a cross sectional view of the structure of the gas turbineaccording to the fifth embodiment of the present invention taken a linein FIG. 5.

FIG. 7 is a schematic view of one example of a conventional gas turbine.

EMBODIMENTS OF THE INVENTION

Hereinafter, embodiments of a gas turbine according to the presentinvention will be described with reference to the accompanying drawings.

Embodiment 1

Hereinafter, the first embodiment of the gas turbine according to thepresent invention will be described.

FIG. 1 is a schematic view of a structure of the first embodiment of thegas turbine according to the present invention.

As shown in FIG. 1, the gas turbine according to the first embodimentcomprises a rotor 10 for rotating around a rotation axis, a plurality ofrotor blades 11 circularly arranged along an outer peripheral surface, aturbine casing 12 for surrounding and covering the rotor 10 and aplurality of stator blades (not shown) arranged at an inner surface ofthe turbine casing 12, wherein the rotor blades and the stator bladesare alternatively arranged along the axial direction of the rotationaxis. As shown in an arrow F in FIG. 1, the main flow of the combustiongas 13 is passed through therebetween. Each rotor blade and each statorblade are formed as one pair along the axial direction. A multi stagestructure is formed by a plurality of pairs of the rotor blades and thestator blades. FIG. 1 shows only a rotor blade of the last stage in themulti stage structure. The rotor blade as shown in FIG. 1 is located atthe lowermost side with respect to a direction of the main flow 13.

At the downstream side of the rotor blade with respect to the directionof the main flow, a rotor blade 11 of the last stage is coaxiallyconnected to an exhaust diffuser 14. The exhaust diffuser 14 comprisesan exhaust casing 16 of which a cross sectional area is graduallyenlarged along the direction of the main flow is formed as a flow of thecombustion gas 15 continued to the main flow of the combustion gas 13, aplurality of struts 18 for surrounding with and supporting a bearing 17for supporting the rotor 10 passed through the exhaust casing 16 andmanholes 19 in which an operator can walk for a check operation and amaintenance operation. At the downstream side of the exhaust diffuser 14with respect to the direction of the flow, a cylindrical exhaust duct 20is coaxially connected to the exhaust diffuser 14.

The first embodiment of the gas turbine provides an air bleeder tube 1for bleeding a portion of the compressed air from a compressor (notshown) and discharging the compressed air into the exhaust duct 20 so asto improve a startup performance of the compressor at a startup timing.

In the gas turbine according to the first embodiment, the air bleedertube 1 is located at a position where the air bleeder tube 1 does notobstruct the main flow of the combustion gas. Thus, the bleeder tube 1is passed through an inside of the manhole 19 and an outlet of the airbleeder tube 1 is arranged in an inner diameter portion 14 a of theexhaust diffuser 14 and directed toward the downstream of the main flow.In the first embodiment, the air bleeder tube 1 is passed through theinside of the manhole 19. However, the air bleeder tube 1 may be passedthough an inside of the strut 18. Alternatively, the air bleeder tube 1may be passed through an existing member connected to the bearing 17 forsupporting the rotor 10 except the members described above.

Accordingly, in accordance with the gas turbine according to the firstembodiment, the main flow of combustion gas is not obstructed in theexhaust duct 20 so that an increase of the pressure loss in the exhaustduct 20 can be saved and the performance of the gas turbine can beimproved.

Embodiment 2

Hereinafter, the second embodiment of the gas turbine of the presentinvention will be described.

FIG. 2 is a schematic view of a structure of the gas turbine accordingto the second embodiment.

As shown in FIG. 2, the gas turbine according to the second embodimenthas a structure similar to the structure of the first embodiment exceptan air bleeder tube 1 located at a position immediately near thedownstream side of a manhole 19 with respect to the direction of theflow not so as to obstruct the main flow of the combustion gas.

Accordingly, in accordance with the gas turbine of the secondembodiment, the main flow of the combustion in the exhaust duct 20 isnot obstructed so that an increase of the pressure loss in the exhaustduct 20 can be saved and the performance of the gas turbine can beimproved.

Embodiment 3

Hereinafter, the third embodiment of the gas turbine of the presentinvention will be described.

FIG. 3 is a schematic view of a structure of the gas turbine accordingto the third embodiment.

As shown in FIG. 3, the gas turbine according to the third embodimenthas a structure similar to the structure of the first embodiment exceptan outlet of air bleeder tube 1 located at a downstream outer edge of amanhole 19 with respect to the rotation axis not so as to obstruct themain flow of the combustion gas.

Accordingly, in accordance with the gas turbine of the third embodiment,the main flow of the combustion gas in the exhaust duct 20 is notobstructed so that an increase of the pressure loss in the exhaust duct20 can be saved and the performance of the gas turbine can be improved.

In the third embodiment, the air bleeder tube 1 is bent at an obtuseangle so as to reduce the pressure loss although the air bleeder tube 1according to the first and second embodiments is bent at a right angle.Thereby, a proper amount of compressed air can be bled from a compressorat startup timing so that a startup performance of the compressor can beimproved.

Embodiment 4

Hereinafter, the fourth embodiment of the gas turbine of the presentinvention will be described.

In order to improve the startup performance of the compressor at thestartup timing, the gas turbine of the fourth embodiment comprises alarge diameter low pressure air bleeder tube 1 (hereinafter, it isreferred as “low pressure air bleeder tube”) connected to a front stageand an intermediate stage of the compressor, and a middle pressure airbleeder tube 1 (hereinafter, it is referred as “middle pressure airbleeder tube”) and a small diameter high pressure air bleeder tube1(hereinafter, it is referred as “high pressure air bleeder tube”)connected to a rear stage of the compressor.

FIG. 4 is a cross sectional view of the structure of the gas turbineaccording to the fourth embodiment of the present invention taken a linealong A-A in FIG. 1.

As shown in FIG. 4, the structure of the gas turbine of the fourthembodiment is similar to the structure of the first embodiment exceptmanholes 19 arranged in an inverted Y shape, wherein the large diameterlow pressure air bleeder tube la and the large diameter middle pressureair bleeder tube lb is passed through two lower side manholes 19 a, 19b, respectively and the small diameter high pressure air bleeder tube 1is passed through a upper side manhole 19 c.

Thus, in the two lower manholes 19 a, 19 b into which an operator canaccess smoothly and in which an operator can work easily, the largediameter low pressure air bleeder tube la and the large diameter middlepressure air bleeder tube lb is passed through, respectively. In theupper manhole in which an operator cannot work easily, the smalldiameter air bleeder tube 1 c is passed through. As the result, aproductive efficiency for manufacturing a gas turbine can be improved.

Although the small diameter high pressure air bleeder tube 1 c is passedthrough the upper manhole 19 c in the fourth embodiment, a smalldiameter high pressure air bleeder tube 1 c may be passed through aredundant space in the two lower manholes 19 a, 19 b in the case thatthe small diameter high pressure air bleeder tube 1 c can be passedthrough the redundant space in the two lower manholes 19 a, 19 b.Although three air bleeder tubes 1 are arranged in the fourthembodiment, one air bleeder tube 1 or a plurality of air bleeder tubes 1such as two, four or more than may be arranged.

In the conventional gas turbine, if a plurality of air bleeder tubes 1such as the large diameter low pressure air bleeder tube 1 a, the largediameter middle pressure air bleeder tube 1 b and the small diameterhigh pressure air bleeder tube 1 c are arranged, the main flow of thecombustion gas is obstructed by these air bleeder tubes 1 and thepressure loss is largely increased. On the contrary, in the gas turbineaccording to the present invention, even if the plurality of air bleedertubes are arranged, the main flow of the combustion gas in the exhaustduct 20 is not obstructed by them. Thus, an increase of the pressureloss in the exhaust duct 20 can be saved and the performance of the gasturbine can be improved.

Embodiment 5

Hereinafter, the fifth embodiment of the gas turbine of the presentinvention will be described.

At the downstream end of the gas turbine with respect to the directionof the flow, an exhaust duct of which a cross sectional shape is arectangular for connecting with a lower side equipment such as a boiler(hereinafter, it is referred as “a rectangular exhaust duct”) may beprovided.

FIG. 5 is a schematic view of a structure of a gas turbine according tothe fifth embodiment according to the present invention. FIG. 6 is across sectional view of the structure of the gas turbine according tothe fifth embodiment of the present invention taken a line B-B in FIG.5.

As shown in FIG. 5, a structure of the gas turbine according to thefifth embodiment is similar to that of the gas turbine according to thefourth embodiment except a rectangular exhaust duct 21 connected to thelower stream side of a cylindrical exhaust duct 20.

As shown in FIG. 6, in the gas turbine according to the fifthembodiment, two outlets for the large diameter low pressure air bleedertube 1 a and the large diameter middle pressure air bleeder tube 1 b isprovided at the both lower sides of the inlet side of the rectangularexhaust duct 21 and one outlet for the small diameter high pressure airbleeder tube 1 c is provided at one upper side of the inlet side of therectangular exhaust duct 21.

As described above, the outlets of the large diameter low pressure andmiddle pressure air bleeder tubes is arranged at the both lower sides ofthe inlet side of the rectangular exhaust duct 21 in which an operatorcan work relatively easily, respectively. The outlet of the smalldiameter high pressure air bleeder tube is arranged at the upper side ofthe inlet side of the rectangular exhaust duct 21 in which an operatorcannot work easily. Thus, the productive efficiency for manufacturingthe gas turbine can be improved.

Although the outlet of the small diameter high pressure air bleeder tube1 c is provided at a upper side corner of an inlet end of therectangular exhaust duct 21 in the fifth embodiment, the small diameterhigh pressure air bleeder tube 1 may be passed through a redundant spaceof the outlets of the large diameter low pressure air bleeder tube 1 aand the large diameter middle air bleeder tube 1 b provided at the lowerside corners of the inlet end of the rectangular exhaust duct 21, ifsuch a redundant space is existed after arranged the both large diameterair bleeder tubes 1 a and 1 b. Although three air bleeder tubes 1 areprovided in the fifth embodiment, it is possible to provide one airbleeder tube 1 or a plurality of air bleeder tubes 1 such as two or fouror more than.

If a plurality of air bleeder tubes 1 such as the large diameter lowpressure air bleeder tube 1 a, the large diameter middle pressure airbleeder tube 1 b and the small diameter high pressure air bleeder tube 1c are provided in a conventional gas turbine, a main flow of thecombustion gas is obstructed by these air bleeder tubes 1. As theresult, the pressure loss is largely increased. In accordance with thegas turbine according to the fifth embodiment, even if the plurality ofair bleeder tubes are provided in the exhaust duct 20, the main flow ofthe combustion gas in the exhaust duct 20 is not obstructed by them.Thus, the increase of the pressure loss in the exhaust duct 20 can besaved and the performance of the gas turbine can be improved.

In the fifth embodiment, the large diameter low pressure air bleedertube 1 a, the large diameter middle pressure tube 1 b and the smalldiameter high pressure air bleeder tube 1 c are bent at an obtuse angleso as to reduce the pressure loss although the air bleeder tubes 1according to the fourth embodiments are bent at a right angle. Thereby,a proper amount of compressed air can be bled from a compressor at astartup timing so that a startup performance of the compressor can beimproved.

INDUSTRIAL USE OF THE INVENTION

In order to improve a startup performance of a compressor at startuptiming, the present invention is applicable to a gas turbine comprisinga compressor and an air bleeder tube, wherein a portion of compressedair is bled from the compressor and bled compressed air is dischargedinto an exhaust duct through the air bleeder tube.

EXPLANATION OF REFERENCE NUMERAL

-   1 air bleeder tube-   1 a low pressure air bleeder tube-   1 b middle pressure air bleeder tube-   1 c high pressure air bleeder tube-   10 rotor-   11 rotor blade-   12 turbine casing-   13 flow of combustion gas-   14 exhaust diffuser-   14 a an inner diameter portion of an exhaust diffuser-   15 flow of combustion gas-   16 exhaust casing-   17 bearing-   18 strut-   19 manhole-   20 exhaust duct-   21 rectangular exhaust duct-   100 air bleeder tube

The invention claimed is:
 1. A gas turbine having a compressor, the gasturbine comprising: an exhaust diffuser; an exhaust duct connected to adownstream side of the exhaust diffuser; and an air bleeder tube thatguides a portion of compressed air bled from said compressor at astartup timing into the exhaust duct, wherein an outlet of the airbleeder tube is configured to direct the portion of the compressed airdownstream of the exhaust diffuser, wherein the compressed air bled fromthe compressor is discharged into the exhaust duct arranged on thedownstream side of the exhaust diffuser, and connected directly to theexhaust diffuser, wherein a main flow of combustion gas is notobstructed by an arrangement of said air bleeder tube, and wherein saidair bleeder tube is passed through an inside of a structural elementconnected to a bearing for supporting a rotor.
 2. A gas turbine asclaimed in claim 1, said gas turbine characterized in that the outlet ofsaid air bleeder tube is arranged at a lower outer peripheral portion ofthe structural element connected to the bearing for supporting therotor.
 3. A gas turbine having a compressor, the gas turbine comprising:an exhaust diffuser; an exhaust duct connected to a downstream side ofthe exhaust diffuser; an air bleeder tube that guides a portion ofcompressed air bled from said compressor at a startup timing into theexhaust duct, wherein an outlet of the air bleeder tube is configured todirect the portion of the compressed air downstream of the exhaustdiffuser; and three structural elements connected to a bearing forsupporting a rotor, wherein said three structural elements are arrangedin an invert Y shape along a peripheral direction of a rotor and saidair bleeder tube is passed through an inside of said three structuralelements, wherein the compressed air bled from the compressor isdischarged into the exhaust duct arranged on the downstream side of theexhaust diffuser, and connected directly to the exhaust diffuser, andwherein a main flow of combustion gas is not obstructed by anarrangement of said air bleeder tube.